<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>css marginwidth marginheight</title>
    <style type="text/css">
    </style>
</head>
<body>
    <iframe src="" cols="50%,50%">
        <iframe src="../html/class.html" marginwidth="0"></iframe>
        <!-- <iframe src="../html/class.html" marginwidth="0"></iframe> -->
    </iframe>
</body>
</html>